Ultrasonic diagnostic apparatuses perform imaging of diagnostic images based on the reflected echo signals outputted from an ultrasonic probe. An ultrasonic probe converts drive signals into ultrasonic waves, and transmits the ultrasonic waves to an object to be examined. A plurality of ultrasonic transducers are disposed in the ultrasonic probe for receiving the reflected echo signals produced from the object and converting them into electrical signals.
In recent years, ultrasonic probes by cMUT have been developed wherein ultrasonic transmission/reception sensitivity, i.e. electromechanical coupling coefficient varies depending on the volume of bias voltage to be applied being overlapped with the drive signals to be provided from an ultrasonic transmission/reception unit. A cMUT is capacitive micromachined ultrasonic transducers manufactured by superconductor microfabrication process. A conventional technique for orthogonalizing an upper electrode and a lower electrode for the purpose of bias control is disclosed, for example, in Patent Document 1.
Patent Document 1: U.S. Pat. No. 6,605,043